Ever since Amazon.com got into the hardware business with the first Kindle monochrome e-reader in 2007, its devices have been seen mainly as a way for the giant e-tailer to effortlessly sell and deliver its digital content to customers. Even when it launched its series of Kindle Fire color tablets, that remained a fair assessment. These color slates did include a limited number of apps and games, plus a browser and messaging. But they still seemed designed primarily to buy and consume e-books, videos and music sold by Amazon.

On Friday, the company is taking another step into hardware with the Amazon Fire phone, and this time things are a bit different. The new phone again has features tightly tied into its online store. But it also includes an unusual new user interface and a premium price that signals that Amazon is serious about becoming a smartphone power, competing head-on with the two leaders in that market, Apple’s iPhone and Samsung’s Galaxy S series.

That new interface, called Dynamic Perspective, attempts to replace the familiar tap-and-swipe navigation with one-handed tilting gestures that expose menus, reveal added information, and scroll the screen.

So how does it stack up against its main premium competitors?

I’ve been testing the Amazon Fire phone since last week, mainly comparing it to the iPhone 5s, which I consider the best smartphone on the market.

I think Amazon deserves credit for creatively trying to change up the familiar tap-and-swipe user experience on phones based on both Apple’s iOS and those, like Samsung’s, that use Google’s Android platform. And the phone is a competent device, with a vivid, crisp display, a very good camera, and dual speakers.

But I consider the Amazon Fire phone no more than an interesting first step. In my tests, I found its big new features less useful than I expected, and sometimes outright frustrating. And, arriving seven years after the debut of the first modern smartphone, Amazon’s new entry lacks some key functions both Apple and Samsung include.

Just One Carrier

Perhaps the biggest problem for this new phone, out of the gate, is that it’s only available on a single carrier, AT&T, and I am led to believe that this exclusivity, while not unlimited, isn’t just a brief promotion. Currently, Amazon doesn’t even have a model that could work on Verizon. Of course, the iPhone famously was exclusive to AT&T for several years, but that was a long time ago, when the whole device category was new. Consumers who don’t like AT&T’s coverage or plans won’t want the Fire.

Premium Price

The Amazon Fire phone will cost $199 with a two-year contract, or $650 without a contract. Those are the same prices AT&T charges for the base iPhone 5s, but the Fire offers twice the storage capacity at those prices — 32 gigabytes versus the iPhone’s 16GB. A 64GB model will cost $100 more. And for an unspecified limited time, Fire buyers get a free one-year subscription to Amazon’s Prime program, which otherwise costs $99.

The Fire has a 4.7-inch screen, compared with four inches on the current iPhones (bigger screens are likely in new iPhones in the fall) and 5.1 inches for Samsung’s Galaxy S5. I found it generally comfortable in the hand.

Dynamic Perspective

The phone’s two big new features are Dynamic Perspective and Firefly. The first is powered by four special sensors, small cameras with infrared LEDs in each corner. These detect the presence and position of a user’s head in relation to the phone.

With Dynamic Perspective, you can tilt your head, or the phone, to see parts of some photos that go beyond the edges of the screen. You can also tilt your head, or the phone, to scroll up and down in some apps. You can also tilt the phone slightly to “peek” at details like icon labels or restaurants on a map.

It was cool to be able to look at things like clothing items on Amazon from all sides. And Dynamic Perspective is a plus when playing games designed to make use of it.

But the most frequent use of the feature is flicking the phone sharply to the left or right to expose information. The screen contents are actually on three panels, and the left and right panels only appear when you do this sharp tilting. They overlap the larger central panel.

Typically, the left panel contains menus, and the right panel has added information. For instance, in email, the left panel lists accounts and mailboxes, while the right panel collects all your attachments for handy use. On the home screen, the left panel lists categories like apps, music, and so forth; the right has the weather, calendar, and some notifications.

It’s a neat trick, but, in my tests, I found that I tired of it, partly because you have to flick the phone just right to make the panels appear, and then again to dismiss them. Call me impatient, but after too many frustrating flicks I resorted to swiping the side panels open and closed, even when I was using the phone one-handed, because I found it quicker and surer.

I was also disappointed with the auto-scrolling. It wasn’t that it didn’t work well — it did. But so far it only works in the Web browser and in lists of book, music and video titles. It doesn’t work, for instance, while reading a Kindle book, though Amazon plans a software update for that in a few months.

Firefly

The other big feature, Firefly, also disappointed. It uses the camera to identify products, books, songs, TV shows, movies, printed email addresses and more. And when it identifies something Amazon sells, it displays the link to let you buy it. Firefly is the shopping-cart feature of the Fire phone, and you launch it by long-pressing on the dedicated camera key on the side.

My problem with Firefly was its inconsistency. One morning, it correctly identified Quaker Oats, but not Cheerios. Dial liquid soap was seen as Dial soap bars. And it never could identify the Samsung Galaxy S5 box. It also got the email address wrong when scanning the business card of an Amazon executive.

But it correctly identified many other things, and did especially well on songs and popular TV shows.

Camera, Calls and Speakers

I found the camera to be very good, with accurate colors and good performance indoors and out. Voice-call clarity wasn’t the best I’ve ever experienced, but it was okay. The twin speakers, oddly, sounded a bit tinny to me and to another person I asked, when compared to the iPhone’s single speaker.

Voice Assistant

The voice assistant did a decent job of recognizing my requests, but it does far fewer things than Apple’s Siri. At launch, it can only make phone calls, send text messages (and have new messages read to you), send emails and search the Web. There’s also a dictation key on the keyboard.

Downsides

In my tests, AT&T’s data-network speeds on the Fire were a tad below Verizon’s on the iPhone. But the big surprise was the Fire’s Wi-Fi speed. When it was near a wireless router, it delivered the full 35 Mbps my service provides. But just a room away, the speed would drop drastically to about a tenth of that. The iPhone remained constant. Amazon says this may have to do with my particular router, and is studying the issue.

Then there is a whole list of features offered by Apple and Samsung that the Fire lacks. Among these are things like fingerprint readers, built-in health sensors, integrated video calling and more. The Fire’s built-in app for viewing Microsoft Office documents can’t edit those documents unless you buy a premium version of the app. And the phone doesn’t support Bluetooth Low Energy, though that’s coming via a software update.

Finally, there are only about 185,000 apps available for the Fire, less than 20 percent of what’s available for Apple and Android phones. Amazon has added a bunch of key apps, but some, like an official YouTube app, are still missing.

Bottom Line

The Amazon Fire phone is perfectly suited for people heavily invested in the company’s ecosystem, and who like to use their smartphones one-handed, as long as they like AT&T. But to top Apple and Samsung, Amazon needs to do better.

The Amazon Fire phone is a competent device with some new twists, but it’s only on one carrier, and lacks some features of competitors.

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